1. Field of the Invention
The present invention relates to a headlamp for a vehicle comprising low beam irradiating means, main beam irradiating means and light distribution switching means for switching a low beam and a main beam.
2. Description of the Related Art
A conventional headlamp for a vehicle comprises low beam irradiating means for emitting light forward, obliquely and downward from a vehicle and illuminating a region at a short distance, thereby forming a low beam which does not become glare light for a vehicle running in the opposite direction, and main beam irradiating means for emitting light in almost parallel with an axle and illuminating a region at a long distance, thereby forming a main beam which is convenient for driving in the case in which the vehicle does not run in the opposite direction, and is constituted such that the low beam and the main beam are switched by light distribution switching means to obtain a light distribution corresponding to a driving situation.
In the conventional headlamp, however, some abnormality might be generated, for example, a light source bulb for a low beam can not be turned on due to a wiring disconnection being happening during a drive with the low beam light. Furthermore, in another case, switching from a main beam to a low beam cannot be carried out with the main beam being held as it is even though switching is actually executed. In the case where such abnormality is generated, the main or high beam shall be kept to be turned on in driving. However, glare light given to a vehicle, which is driving in the opposite direction, is not preferable in respect of safety.
There is a solution for such a problem using a technique for attenuating a main beam so as not to generate a glare light. However, the amount of light of the main beam is consequently decreased so that a visibility becomes reduced. Therefore, the technique is eventually not safe in respect of driving condition.
Taking these problems into consideration, it is an object of the invention to provide a headlamp for a vehicle capable of maintaining a visibility in a forward direction of a vehicle and forming a proper light distribution which does not produce a glare light for a vehicle driving in the opposite direction by turning on the main beam (or switching a light distribution by a low beam to that of the main beam) when some abnormality is generated over a light distribution for the low beam.
In order to achieve the object, a first aspect of the invention is directed to a headlamp for a vehicle comprising low beam irradiating means, main beam irradiating means, light distribution switching means for switching a low beam and a main beam, abnormality detecting means for detecting an abnormal situation in which a proper low beam cannot be formed, and optical axis tilting means for vertically tilting an optical axis of at least a main beam,
wherein in the case wehere the abnormality detecting means detects the abnormal situation, the light distribution switching means can be driven if necessary and the optical axis tilting means can be driven to turn the optical axis of the main beam downward, said main beam being turned on or energized.
For the optical axis tilting means, a tilting mechanism for vertically tilting the optical axis of the lamp can be proposed. In the case in which serious troubles in which a proper low beam cannot be formed are made by the abnormality detecting means, a driver recognizes the serious troubles through the abnormality display means such as a warning light. There are the cases in which a light distribution is manually switched into the main beam if necessary and the optical axis tilting mechanism is driven to turn the main beam downward and the case in which the light distribution switching means is automatically driven and the optical axis tilting mechanism is automatically driven if necessary in connection with the abnormality detection of the abnormality detecting means.
According to a second aspect of the invention, in the case in which a low beam is turned on in a headlamp extinction state or an abnormal situation is detected during lighting of the low beam, a light distribution is switched into a main beam by the light distribution switching means and an optical axis of the main beam is turned downward by the optical axis tilting means, and in the case in which an abnormal situation is detected when the light distribution is to be switched from the main beam to the low beam, the light distribution is maintained as it is or the light distribution is returned to the main beam by the light distribution switching means, and the light distribution or the optical axis of the light distribution of the main beam is turned downward.
More specifically, a first case in which the low beam is turned on when the headlamp is put out, a second case in which the low beam is being turned on, and a third case in which a light distribution is switched from the main beam to the low beam can be proposed for a period in which the serious troubles are detected. In the first case, the low beam is not turned on at all. In the second case, the low beam is turned off during lighting. In both cases, when these situations are detected by the abnormality detecting means, the light distribution can be switched into the main beam by the light distribution switching means and the optical axis of the main beam can be turned downward by the optical axis tilting means.
Moreover, the third case includes the case in which lighting is not vehicleried out when the light distribution is switched from the main beam to the low beam by the light distribution switching means (first and second embodiments) and the case in which the light distribution switching means cannot be driven as is expected (third, fourth and fifth embodiments). When these situations are detected by the abnormality detecting means, the light distribution is returned to the main beam by the light distribution switching means or the optical axis of the main beam is turned downward by the optical axis tilting means with the light distribution maintained. (Function) For example, in the case in which some abnormality is generated so that a proper low beam cannot be formed, that is, a light source bulb for a low beam cannot be turned on due to a disconnection during driving with the low beam turned on or the light distribution cannot be switched (the main beam is maintained) although the switching from the main beam to the low beam is vehicleried out by the light distribution switching means, the light distribution is set to be the main beam in principle. Since the main beam generally has a larger light amount than that of the low beam, a visibility in the forward direction of a vehicle can be maintained. Moreover, the main beam is light which is almost parallel with an axle and can become glare light for a vehicle driving in the opposite direction. By turning the optical axis of the main beam downward, however, a countermeasure can be taken to prevent the glare light from being generated.
A third aspect of the invention is directed to the headlamp for a vehicle according to the first or second aspect of the invention, wherein the low beam irradiating means is constituted by a reflector for a low beam and a light source for a low beam, and the main beam irradiating means is constituted by a reflector for a main beam and a light source for a main beam, and
the light distribution switching means is constituted by a circuit for switching power supply to each of the light sources of the two beam irradiating means.
(Function) The low beam irradiating means and the main beam irradiating means are constituted by the separate reflector and light source, respectively. Therefore, large light amounts can be maintained respectively, and furthermore, both reflectors can easily be provided adjacently and can also have simple structures. Since the light distribution switching means is constituted by the circuit for switching the power supply to the respective light sources and a mechanical driving section is not provided, moreover, it is small-sized and has a light weight, and rarely causes failures.
A fourth aspect of the invention is directed to the headlamp for a vehicle according to the third aspect of the invention, wherein the reflector for a low beam and the reflector for a main beam are constituted by a single reflector having a reflecting surface for a low beam and a reflecting surface for a main beam, and the light source for a low beam and the light source for a main beam are constituted by a single light source bulb having a pair of built-in filaments (a front filament for a low beam, a shade for light distribution control for shielding a part of the light emission of the filament, and a rear filament for a main beam) which are provided apart from each other in an axial direction.
(Function) The low beam irradiating means and the main beam irradiating means are constituted by the single light source inserted and attached into the single reflector. Therefore, the size of the whole headlamp can be reduced correspondingly.
A fifth aspect of the invention is directed to the headlamp for a vehicle according to the first or second aspect of the invention, wherein the low beam irradiating means and the main beam irradiating means are constituted with a single reflector, a single light source and a single shade for light distribution control integrated with each other, and the light distribution switching means is constituted such that any of the reflector, the light source and the shade for light distribution control is driven to switch a light distribution. A discharge bulb capable of obtaining a larger light amount than that of an incandescent bulb is desirable for the single light source to be inserted and attached into the single reflector.
(Function) The single reflector, the single light source and the single shade for light distribution control are integrated to constitute the low beam irradiating means and the main beam irradiating means. Consequently, the size of the whole headlamp can be reduced correspondingly.
When a part of the reflector is tilted longitudinally with respect to the light source and the shade, the optical axis of the reflector (the optical axis of reflected light on the reflector) is changed vertically. When the light source is tilted vertically with respect to the reflector and the shade, the optical axis of the reflector (the optical axis of the reflected light on the reflector) is changed vertically. When the shade for light distribution control is moved longitudinally with respect to the reflector and the light source, the effective reflecting surface region of the reflector is changed so that the optical axis of the reflected light is changed vertically.
A sixth aspect of the invention is directed to the headlamp for a vehicle according to any of the first to fifth aspects of the invention, wherein the headlamp comprises an auto-leveling device for carrying out a vertical tilt and regulation such that the optical axis of the lamp has a constant configuration with respect to a road based on a detection value of a vehicle sensor, an optical axis tilting mechanism of the auto-leveling device and a control section for controlling a driving operation thereof constituting the optical axis tilting means.
(Function) In the headlamp comprising the auto-leveling device for carrying out a tilt and regulation such that the optical axis of the lamp has a constant configuration with respect to a driving road, (the optical axis tilting mechanism and the control section for controlling a driving operation thereof) of the auto-leveling device is used as the optical axis tilting means for vertically tilting the optical axis of the main beam. Consequently, the optical axis tilting means of the main beam does not need to be provided separately.